My friend who has a Z-28 with a 5spd always keeps the pedel down when at a stop or in traffic,I told him this causes wear on his throwout bearing also when driving he keeps his foot lightly on the clutch pedal,I,m on my second clutch in 15 years,he is on his 6th.Am I busting him for nothing or is this the cause of his problems.Both these cars are not really beat on.

 

You are correct. Pushing the clutch always wears the throwout bearing out more.

The worst thing though is riding the clutch while driving down the street. I recall an experiment performed by a taxi company some years ago (when taxis had stick shifts!); they mounted a switch like a brake light switch on the clutch pedal, such that a big obnoxious light on the dash lit up whenever the pedal was depressed however slightly... they nearly doubled their fleet average clutch life. That's fleet average! Just think how many clutched the more serious offenders had to have been going through.

FYI, I get about 60-70k out of clutches in my car, and I think I really abuse them... but I never ever rest my foot on the pedal, and always take off with the engine RPM as low as possible, and let the clutch lock up as quickly as possible.

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"So many Mustangs, so little time..."

 

Another thing to consider at the stop light: With the clutch pedal depressed, the force on the throwout bearing and clutch fingers has to be countered by something. That something is the engine's crank thrust bearing.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.73 unlimited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LB9 w/ZZ3 cam, TBD heads, exhaust, paint, etc.).
57 Bel Air, my 1st car. 0.030 over 396, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

 

The items all mentioned above are of minimum wear to a clutch assembly. If you're going to be at a stop light for 40 minutes then slapping it into neutral is better. Cars aren't perfectly designed. If you put wear on one part you usually save the wear on another part. If you keep in neutral you put extra wear on the input shaft bearing. If clutches were to have frequent deaths from bad TO bearings and worn out diaphram springs it'd be a different story. However most are ruined by riding the clutch and worst of all is using the clutch as a brake on a hill. This is my dad's favorite "skill" of driving stick. I'm glad I don't have to pay for his automotive work.

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1984 WS6 Trans Am Hartop
Former L69 Car under restoration
1984 WS6 Trans Am T-top car
4-bolt main 350, headers, Holley 650, T-5 and 3.23's.
Daily driver and restoration

 

84, if you look back at the original post, he said his friend keeps his foot lightly on the clutch pedal while driving. That's "riding the clutch".

The throwout bearing is a greased, sealed bearing, not designed for continious use. When it goes, it takes often takes other things with it. Input shaft bearings are continously lubed, designed for constant and loaded use. Although the thrust bearing is also continously lubed, it is not designed for continous load such as having the clutch pedal depressed all the time.

I'll agree with you, though, that excessive slippage will wear the friction parts out quickly. But then, RB said that in effect, too.

Tom, keep on bustin' him. 3X clutch replacement should be evidence enough.

 

I'm going to have to respectfully disagree with you that the wear caused by being a stop with the clutch pedal depressed is more than minimal and the the engine will surely die of something other than the thrust bearing. While TO bearings are usually trashed by the time clutch changes come the clutch plate is usually what was on it's last legs to be replaced.


I know the way I stated it sounded like I didn't read, but I did take that into account.

The pilot bushing isn't constantly lubricated any more than the throw-out bearing. My point is aside from any partial release of the clutch all wear is normal and minimum.

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1984 WS6 Trans Am Hartop
Former L69 Car under restoration
1984 WS6 Trans Am T-top car
4-bolt main 350, headers, Holley 650, T-5 and 3.23's.
Daily driver and restoration